ASHRAE Guideline 13 — Alarm Management

ASHRAE 90.1-2019, Table 6.5.1.1.3

ASHRAE 90.1 Table 6.5.1.1.3 specifies fixed dry-bulb high-limit shutoff temperatures by climate zone. For Climate Zone 4A, the fixed dry-bulb limit is 75 degrees F. This setup correctly locks out the economizer when outdoor air is too warm to provide free cooling. Differential enthalpy is an alternative method.

ASHRAE 90.4 / TIA-942

Branch circuit monitoring is required for capacity planning and to detect load imbalances. ASHRAE 90.4 mandates metering of electrical distribution in data centers, and most Tier III+ designs require per-circuit monitoring.

ASHRAE Fundamentals Handbook — Hydronic System Design

The decoupler (common) pipe connections must be spaced at least 4 to 6 pipe diameters apart so primary and secondary loops are genuinely hydraulically decoupled; at 2 diameters the two loops interact and flow in the common pipe no longer reflects the true surplus or deficit. Note what is NOT the defect here: the absence of isolation valves on the decoupler is CORRECT as installed — valving the common pipe would defeat decoupling entirely.

ASHRAE Guideline 13 — Data Management

Storing trend data only in field controllers risks data loss when controllers are reset or lose power. Trend data should be archived to the BAS server or a dedicated historian. Controller memory is limited and will overwrite oldest data.

ASHRAE Guideline 13, Specifying Building Automation Systems (advisory) — applied through the project BAS specification, Division 25

The installed sensors meet the specification. ASHRAE Guideline 13 (advisory, applied via the project BAS specification) recommends space temperature sensors with accuracy of +/- 0.5 degrees F or better for zone control. The 10K thermistor is a standard sensor type for DDC systems, providing adequate accuracy for HVAC zone control.

ASHRAE Guideline 36 — Chiller Staging

Staging a lag chiller immediately at 100% lead capacity causes hunting and instability. A time delay (typically 10-15 minutes) and sustained load confirmation are required to prevent short-cycling. ASHRAE Guideline 36 specifies staging criteria with time delays and load verification.